This disclosure relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in an example described below, more particularly provides optical push-pull interferometric sensors for electromagnetic sensing.
It can be useful to monitor a subterranean reservoir over time, in order to detect changes in the reservoir. For example, in conventional and enhanced oil recovery, processes such as water flooding, steam flooding and chemical flooding can be implemented. It is useful to monitor injection of water, steam or chemicals into a formation, and/or to monitor progress of the water, steam or chemicals toward or away from one or more wellbores. Monitoring a flood front helps avoid flood breakthroughs, and thereby optimize hydrocarbon production, and can also save costs by reducing an amount of steam, water and/or chemicals used.
Therefore, it will be appreciated that improvements are continually needed in the art of monitoring changes in subterranean reservoirs. Such improvements may be used for monitoring flood front progress, for monitoring other changes in an earth formation, or for other purposes.